The conditions under which a bottle of wine is stored are critical to the wine aging properly. If the wine is not stored properly, it may age too rapidly or develop undesirable bacteria within the wine, spoiling the wine even though the wine bottle is sealed. A typical method to seal the bottle is using a cork. A cork acts as semi-permeable membranes to permit vapor, and in some instances liquid, to pass through the cork. As such, if the vapor pressure is greater inside the wine bottle than outside, the vapor inside the wine bottle will escape through the cork until the pressure is equalized. Conversely, if the vapor pressure is greater outside the bottle, vapor will tend to enter the bottle through the cork until the pressure is equalized. Ideally, the wine should be stored so that vapor escapes from the wine bottle through the cork in a controlled manner. Storing wine bottles in an environmentally controlled wine cellar is considered an optimal technique to age the wine, where environmentally controlled means maintain the air temperature and relative humidity within the wine cellar at desired values.
Wine cellars are used in a wide variety of situations, such as wine retailers, and restaurants. In addition, many individuals collect and store wines within their homes, requiring custom-built wine cellars. Although these custom-built wine cellars vary in their features, they commonly have a single entrance door, which when closed substantially seals the wine cellar from its surrounding environment. They also typically include interior lighting, storage bins, and possibly a table and chairs. Depending on the size of the individual's wine collection, these wine cellars may hold from several hundred bottles of wine to tens of thousands of bottles of wine. This large number of bottles represents a sizable investment by the individual, so proper aging of the wine is critical to achieving a satisfying return on that investment.
Wines produced in Burgundy and Bordeaux, France are stored in caves which have a year-round temperature of about 55.degree. F. This temperature appears to be an ideal temperature to produce and store wines in general. Therefore, to match the conditions under which wines have historically been stored in caves, most wine cellars are maintained between 50-60.degree. F. It has also been found that maintaining the relative humidity within the wine cellar in the range of about 65-80% is desirable so that vapor within the wine bottle will not escape at an accelerated rate. For instance, if the relative humidity in the wine cellar is maintained at a relatively low relative humidity, such as 25%, the vapor generated inside the wine bottle will permeate through the cork and into the wine cellar. This undesirable process will upset the critical chemical balance of the wine, resulting in an ill-tasting wine. In contrast, a relative humidity of about 100% should not be maintained because it will ultimately lead to mold growing on the labels of the individual wine bottles disfiguring their appearance. Although this high humidity does not harm the wine, the moldy labels will certainly lessen the wine bottle's visual appeal.
It is also essential in storing wine that the temperature not only be at a desired value but also that the temperature be maintained relatively constant. If the temperature is allowed to fluctuate widely, the wine will age too rapidly, significantly influencing the taste of the wine, usually for the worse. It is critical, therefore, that the temperature and relative humidity be maintained as constant as possible and allowed to fluctuate only within fairly tight ranges.
To maintain the proper air temperature and relative humidity within a wine cellar, a system is required to cool the air within the wine cellar as well as humidify and, if necessary, dehumidify the air to maintain the proper relative humidity. Conventional environmental control systems are not ideally suited to achieve and maintain the desired air temperature and relative humidity simultaneously. For instance, a standard air conditioning unit can provide air temperatures in the range of 65-78.degree. F., with a resulting relative humidity of about 20-30%. A standard air conditioning unit is not capable of humidifying the air to raise the relative humidity while it operates to cool the air. A refrigeration system can generate temperatures between 33-50.degree. F., with a resulting relative humidity of about 10-15%. A standard humidification unit which uses a humidistat to measure the relative humidity in an enclosure, adds moisture within the enclosure when required. The humidification unit, however, cannot dehumidify or reduce the relative humidity in the enclosure. Typically, dehumidification must be provided by a separate system. Consequently, an environmental control system for maintaining the ideal air temperature and relative humidity in a wine cellar would require the installation of three separate known systems, yielding a complicated and expensive system.
What is needed, therefore, is a single environmental system which is able to control the air temperature within the wine cellar in a relatively tight range, preferably between 54-57.degree. F. as well as a relative humidity range preferably between 70-80%. Such a system would be required to operate continuously and economically to maintain the temperature and relative humidity within these narrow ranges.